I believe that they were doing it to protect secret military payloads.. Keep in mind that this was during the Cold War between USA and Russia...
Also, if not mistaken, they were also patrolling the Atlantic for Russian Trawlers that might have had some weaponry that could have affected the launch.. ie. Lasers and such. At least that's was the scuttlebutt that I'd heard when I was stationed at PAFB for almost 10 years.. And the AC-130's and crew (also, if not mistaken, they were from Hurlburt Fld, FL) were quite nice to talk to as they shared our ramp with the other aircraft that we had at the time (O-2A, OV-10A, OT-37B)...